Document how I use .gitattributes to clean git diffs.

.gitattributes

@@ -0,0 +1,11 @@
+# Usefull with:
+#
+#    cat <<EOF > ~/.local/bin/podiff
+#    #!/bin/sh
+#    grep -v '^#:' "$1"
+#    EOF
+#    chmod a+x ~/.local/bin/podiff
+#    git config diff.podiff.textconv podiff
+
+*.po diff=podiff
+*.pot diff=podiff

README.rst

@@ -190,6 +190,26 @@ became the official french Python documentation translation thanks to
 `PEP 545 <https://www.python.org/dev/peps/pep-0545/>`_.
 
 
+Simplify git diffs
+------------------
+
+Git diffs are often crowded with useless line number changes, like:
+
+    -#: ../Doc/library/signal.rst:406
+    +#: ../Doc/library/signal.rst:408
+
+To tell git they are not usefull information, you can do the following
+after ensuring ``~/.local/bin/`` is in your ``PATH``.
+
+    cat <<EOF > ~/.local/bin/podiff
+    #!/bin/sh
+    grep -v '^#:' "$1"
+    EOF
+
+    chmod a+x ~/.local/bin/podiff
+
+    git config diff.podiff.textconv podiff
+
 Maintenance
 -----------